In the UK, public access to emerging biotechnologies is largely regulated by three government bodies that operate at arm's length from democratically elected representatives: the Human Fertilisation and Embryology Authority (HFEA), the National Institute for Health and Care Excellence (NICE), and the Medicines and Healthcare Products Regulatory Agency (MHRA). Purposefully situated beyond traditional lines of electoral accountability, how can these independent bodies (commonly referred to as 'quangos') conceptualize and demonstrate their accountability to the public in regulating technically complex and morally controversial technologies? After articulating this general theoretical tension between independent and accountable decision-making in the arm's length context, I illustrate how it generates distinct, practical challenges within the HFEA, NICE and the MHRA. To navigate this general tension and address its practical ramifications, I invoke political theories of public reason and deliberative democracy, as well as recent attempts to apply these theories to the governance of biotechnologies. Through a critical analysis of these accounts, I articulate a new framework for 'public accountability as reciprocity' in the arm's length context. Its four, process-oriented conditions, of 1) reciprocal reasoning, 2) acceptance of deliberative disagreement, 3) voting, and 4) fostering the means of deliberative resistance, affirm the goal of identifying mutually acceptable reasons for collective decisions, but take seriously the fact that characteristics of emerging biotechnologies will often confound such attempts. Taken together, these conditions provide a more theoretically robust and normatively legitimate approach than existing accounts, notably 'accountability for reasonableness.' Next, I translate the theoretical claims of this framework into practice, illustrating how its conditions may be fruitfully applied towards the resolution of the practical challenges identified within the HFEA, NICE, and MHRA. In the HFEA, public accountability as reciprocity provides a robust approach to moral reasoning in the body's deliberations and resituates the role of public consultation. In NICE, it suggests a justifiable and properly tailored role for patient involvement in technology appraisals. Finally, in the MHRA, it explains why a growing number of devices defy the institution's traditional assessments of safety and effectiveness and offers reforms to its regulatory boundaries. I conclude with a set of policy recommendations for creating and operating arm's length bodies, as well as an account of broader contributions to the literature on public reasoning, the concept of 'ethics expertise,' and the practice of patient and public involvement.